Diabetic retinopathy is one of the long-term complications of diabetes. The retina is the most important structure of the eye for vision, as it is responsible for capturing the image we see and, through the optic nerve, transferring it to the brain and interpreting it. Therefore, a deterioration in the retina, in this case due to diabetes, will produce a deterioration in vision that can become significant and permanent.
According to the International Diabetes Federation, there are currently 415 million people diagnosed with diabetes and it is estimated that by the year 2040 this figure will increase to 640 million; this is aggravated by the fact that 1 out of every 2 adults with diabetes is undiagnosed, which is a major social, health and economic problem.
That is why it is important to keep in mind that the management of diabetes and its complications begins in primary health care, which should include screening for diabetic retinopathy, and that early detection and timely treatment of diabetic retinopathy can prevent vision loss.
What are the causes of diabetic retinopathy?
It is caused by damage to the body’s blood vessels and, therefore, also to those that nourish the retina, and this occurs as a consequence of high blood glucose levels maintained over a long period of time.
Diabetes produces two types of vascular lesions in the retina:
- Increased permeability of the small blood vessels, which causes fluid to leak out of them, leading to retinal edema which, when it affects the macula (center of the retina), is called macular edema and produces an alteration of the patient’s central vision.
- Hemorrhages that may remain limited to the retina or extend to the gel-like contents of the eye (vitreous humor).
What are the symptoms of diabetic retinopathy?
In the early stages of diabetic retinopathy, the lack of symptoms may cause it to go unnoticed. Among the symptoms that may appear are:
- Decreased night vision
- Alterations in color vision (mainly blue and yellow).
- Poor recovery of vision after exposure to bright light.
- Variation of vision
- Blurred vision
- Episodes of double vision
In advanced stages, the most important symptom is the loss of vision that the patient notices; this loss of vision can be noticed in the center of the image due to diabetic macular edema or even a total loss due to a massive hemorrhage in the vitreous humor.
It should be noted that, for symptoms to appear, the pathology must be in advanced stages, but in this situation the treatment is not as effective. For this reason it is better to control retinopathy before symptoms appear.
What types of diabetic retinopathy are there?
Diabetic retinopathy has different stages:
1. No apparent retinopathy: its appearance is normal, since no lesions are observed in the fundus.
2. Mild non-proliferative diabetic retinopathy: small rounded red dots called microaneurysms can be observed.
3. Moderate non-proliferative diabetic retinopathy: it presents small retinal hemorrhages, as well as white spots or exudates.
4. Severe non-proliferative diabetic retinopathy: occlusive vascular lesions and intraretinal hemorrhages are formed throughout the retina, which stimulates the appearance of new fragile retinal vessels and their extension throughout the retina.
5. Proliferative diabetic retinopathy: the new retinal vessels rupture and cause hemorrhages in the vitreous humor, which stimulate the formation of cicatricial flanges, with traction of the retina and the consequent appearance of retinal detachments.
How can diabetic retinopathy be diagnosed?
It is very important that every person who has been diagnosed with diabetes goes to the ophthalmologist for a check-up at that moment and that this is repeated annually or biannually depending on the evolution of the diabetes.
The ophthalmologic examination should include the following tests:
Eye examination: central vision, visual acuity, ocular tension and the anterior surface of the eye are measured.
Fundus examination: consists of dilating the pupil to better analyze the more peripheral areas of the retina. The examination can be performed with different instruments, such as the hand-held ophthalmoscope (direct ophthalmoscopy) or the binocular ophthalmoscope (indirect ophthalmoscopy), and with examination lenses that are placed over the eye and are aided by the use of the lamp or a retinograph to file the image of the eye.
Fluorescein angiography: allows visualization of the deep vascular network of the eye. It is performed when there are lesions in the fundus of the eye.
Optical coherence tomography (OCT): it is a technique that captures a very accurate image of the different layers of the retina. It is very useful in cases of macular edema.
What is the treatment of diabetic retinopathy?
As mentioned above, it should be kept in mind that early diagnosis and treatment can prevent vision loss, i.e., a person with diabetes can live his whole life without eye problems as long as he is under proper ophthalmologic control and knows how to live with this disease (medication, healthy diet and adequate physical activity).
Thus, in the early stages of the disease, the only treatment is the control of diabetes. When significant vascular alterations have already been detected, treatment consists of laser photocoagulation, which helps to stabilize retinopathy by reducing abnormal and fragile blood vessels and preventing further hemorrhages, but not to cure it.
When macular edema appears, it cannot be treated with laser, so it requires a very specific medication (anti-VEGF or dexamethasone) which is administered by injections into the eye.
Finally, if there is an alteration in the vitreous humor, either by flanges that can move the retina or by repeated hemorrhages, the treatment is surgical, specifically by means of a technique called vitrectomy, which consists of removing the vitreous humor opacified by blood.